Radio frequency identification (RFID) readers may be used in, for example, retail environments to keep track of merchandise tagged with RFID tags, with a goal of ensuring that merchandise in inventory is properly displayed on the sales floor. It is very important to retailers to make sure their sales floor shelves are never empty, especially if there is merchandise in the back of the store that can be used for replenishment. Currently, retailers often do not know that replenishment is needed, so stores miss sales opportunities when merchandise in the back room should instead be on the empty sales floor shelves. RFID readers are typically configured to read RFID tags within a predefined range and are effective in detecting new merchandise introduced on the sales floor. However, RFID readers are not as effective in tracking merchandise already on the sales floor, and knowing the accurate shelf count is critical so replenishment happens at the appropriate time. Simply removing an item from the shelf is no guarantee that it will be purchased, so the shelf's inventory count should not be automatically reduced in this situation. For example, when an item is removed from a shelf, the item may be moved to another location in the store and left there or it may be returned later to its proper shelf location. If the item is purchased and removed from the store, existing point of sales systems may automatically reduce the inventory count for that item, providing an indication that the item needs to be replenished. However, when the item is moved to another location in the store, the item may not be easily located and returned to the proper shelf. To avoid missing sales opportunities, it is critical not only to know the merchandise currently in a store's total inventory, but also know the accurate breakdown of shelf inventory on the sales floor versus back room inventory as well as know which merchandise is improperly shelved on the sales floor.
Attempts made to track the specific locations of tagged merchandise using RFID readers as the tagged merchandise moves through a store have shown to be near or beyond the limits of RFID technology. Department level tracking is therefore a desirable alternative to tracking the specific locations of tagged merchandise as the merchandise moves through a store because when it can be confirmed that an item has been moved from a region of the store (also referred to as a department) where the item is meant to be properly shelved, there is a higher level of certainty that the item is no longer properly shelved. However, prior attempts at department level tracking have resulted in either an excessive amount of data, which is extremely difficult to manage, or not enough data.
In RFID protocol, there are four sessions, sessions 0, 1, 2, and 3, and two states, state A and state B. By default, an unread RFID tag is in state A, and once the tag is read, the tag may be switched to the B state, depending on the session. Once shelved, the majority of tagged items are not moved around and do need to be read repetitively. However, in session 0, the RFID reader reads an RFID tag over and over until the RFID tag is out of range or shielded from the RFID reader, creating an excessive amount of data and potentially preventing tags closer to the edges of the reader's range from being read. Session 1 is similar to session 0 except that in session 1 when an RFID tag is read by the RFID reader, the tag will not be read again for a predefined period. For example, the tag will not be read for the next one and a half seconds. Accordingly, in session 1, tagged items may be read every one and a half seconds, also creating an excessive amount of data. The vast majority of these tags don't need to be read repetitively since nothing of significance is happening to them. This exorbitant amount of unnecessary data can be difficult to manage.
In sessions 2 and 3, when the tagged item is read, the state is switched from state A to state B and the tag stays in state B if it can detect RF power within a defined period, for example, five to fifteen seconds. While the tag is in state B, the tag won't be read again by the RFID reader, reducing the amount of data provided by the RFID reader. If the tag is switched from state A to state B and the tag does not detect radio frequency (RF) power after more than, for example, fifteen seconds, the tag is switched back to state A. Using this approach, the tag may only be read once if RF power is constantly detectable, potentially producing insufficient data. In other words, the tag won't be tracked beyond its first and only read.
Another approach utilizes a checkerboard of alternating readers (or alternating antennas within a reader), wherein an RFID reader (or antenna) configured to read in session/state 3A, for example, switches a tag from 3A to 3B after reading the tag, and another RFID reader (or antenna) configured to read in session/state 3B switches the tag to state 3A after reading the tag. The intent is that as a tagged item moves through a space, it will be read once by the 3A reader and the tag state will be flipped to 3B so that when the tag is then in the range of 3B reader, the tag will be read by the 3B reader and the tag state will be flipped back to 3A, and so on. However, coverage in the 3B regions may not be acceptable because a prerequisite of a tag being read by the 3B reader is that the tag was previously read by a 3A reader and the tag did not lose RF power for more than a predefined period, for example, 5 seconds, before entering the 3B region. RF power typically may not cover one hundred percent of a space. As such, there may be natural nulls, RF hidden spots, for example, under metal shelves and next to people, and/or tag shadowing. Using this approach, if an RFID tag is not switched to the 3B state because it was not read by a 3A reader or because it cannot detect RF power for a predefined period after being read by a 3A reader, the 3B readers will not be utilized to their full potential, creating unwanted holes in RF coverage and again providing insufficient data.
Accordingly, there is a need for an apparatus and method for balancing the number of RFID reads to produce an appropriate quantity of data.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.